1. Field of the Invention
The present invention relates to an insertion device, a lithographic apparatus and a device manufacturing method. In particular, the present invention relates to an insertion device configured to insert an object into a conditioned environment.
2. Description of the Related Art
Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device may be used to generate a desired circuit pattern corresponding to an individual layer of the IC, and this pattern can be imaged onto a target portion (e.g. comprising one or more dies) on a substrate (silicon wafer) that has been coated with a layer of radiation-sensitive material (resist).
In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion in one go, and so-called scanners, in which each target portion is irradiated by scanning the pattern through the projection beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
In a prior art lithographic apparatus, the imaging of the circuit pattern onto the target portion is performed within a conditioned environment, such as, for example, within a chamber with reduced pressure (e.g., vacuum). To project an image onto the substrate, the substrate needs to be positioned within the conditioned environment. Inserting the substrate into the conditioned environment is performed by using a conditionable vessel which contains a conditionable interior. That is, the vessel interior may be configured with the capability of adjusting the pressure inside the vessel and/or controlling the number of particles present inside the vessel. The conditionable vessel may be part of an insertion device. Note that such an insertion device, as well as the conditionable vessel, may not only be employed inserting the substrate into the conditioned environment, but may also be employed for removing the substrate from the conditioned environment. Also, the conditionable vessel or the insertion device may be employed for other objects than a substrate such as a patterning device, for example.
A conditionable vessel is typically positioned between the conditioned environment and the outside (e.g. atmospheric environment) and functions as an intermediate chamber. The conditions inside the intermediate chamber (i.e. within the interior of the vessel), may vary. When an object is to be loaded into the conditioned environment of the lithographic apparatus, the object is first loaded into the intermediate chamber through a first gate in the vessel, whereby the intermediate chamber is subjected to atmospheric conditions and/or dust particles. After closure of the first gate, the interior of the vessel is conditioned such that the conditions are substantially equal to the conditions in the conditioned environment of the lithographic apparatus. Then, a second gate in the vessel connecting the interior of the vessel with the conditioned environment of the lithographic apparatus may be opened and the object may be transferred from the vessel to the lithographic apparatus.
To transfer the object from the atmospheric environment to the conditioned environment, a robot arm may be positioned in the atmospheric environment to transfer the substrate from the atmospheric environment through the first gate into the vessel. Inside the vessel, the object is positioned on a pad or the like. Then, after closing the first gate of the vessel, the environmental conditions inside the vessel may be changed such that they correspond to the environmental conditions of the conditioned environment.
A robot arm inside the conditionable vessel then transfers the object from said pad or the like into the conditioned environment through the second gate. To the robot arm, there is connected an object support pad for carrying the object. A robot arm trajectory is therefore to be set to transfer the object support pad and the object thereon through the second gate. Moving the object support pad through the first or the second gate requires a highly accurate movement along said robot arm trajectory. Therefore, it is required to minimize any disturbance of the trajectory of the robot arm and object support pad to ensure a transfer through the gate and an accurate positioning of the object.
The first gate and the second gate may be the same gate. However, to transfer the object from a first environment to a second environment, the environment outside the conditionable vessel needs to be changed from the first to the second environment while the object is inside the conditionable vessel. For example, the gate of the conditionable vessel may be repositioned with respect to the first and second environment, while the interior of the vessel having the object therein is being conditioned.
Generally, a robot controlling the robot arm is attached to the outside of the vessel and position the robot arm and the object support pad inside the vessel through an opening in the vessel wall. During production of the vessel, the robot is mounted on the vessel wall and the robot arm trajectory is set with respect to the vessel, in particular with respect to the gate through which the robot arm is going to transfer the object, as mentioned above.
After production of the insertion device comprising the conditionable vessel and robot, it is no longer possible to adjust the trajectory of the robot arm and object support pad without opening the vessel. However, if the trajectory gets disturbed, the vessel needs to be opened to reset the trajectory. Opening the vessel may be difficult due to a complex construction, which has been designed to create the conditioned interior, such as, for example, the creation of a gas-tight vessel construction. After adjustment, the interior may need to be reconditioned, rendering the adjustment procedure not only difficult, but also time-consuming and expensive.
Since the vessel wall may undergo a deformation, such as when the pressure inside the vessel is reduced, because the robot is attached to the outside of the vessel, the orientation and position of the robot, as well as the robot arm and its trajectory, may be disturbed due to the vessel wall deformation. Generally, to minimize the disturbance of the robot arm trajectory, the robot is positioned in the center of the vessel wall. Due to the reduced pressure inside the vessel, the vessel wall becomes concave. In the center, the vessel wall keeps its orientation, and thus the orientation of the robot arm will not be changed when the vessel wall deforms due to the reduced pressure inside the vessel.
Positioning the robot in the center of a vessel wall, however, limits the design of the vessel. To reduce the size of the vessel, thereby requiring less space, it has been found that it is advantageous to position the robot asymmetrically, i.e. not in the center, with respect to the vessel wall.